Short Communication: Volatiles in microfluidized raw and heat-treated milk

Authors: Van Hekken, Diane; Iandola, Susan

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2019
Publication Date: 8/1/2019
Citation: Van Hekken, D.L., Iandola, S.K. 2019. Short Communication: Volatiles in microfluidized raw and heat-treated milk. Journal of Dairy Science. 102:8819-8824. https://doi.org/10.3168/jds.2018-15776.
DOI: https://doi.org/10.3168/jds.2018-15776

Interpretive Summary: Milk, a nutritious food that is a staple in the American diet, has a bland flavor and slight aroma. The aroma of milk can begin to change with common dairy processing steps, which can be desirable in some products and unwanted in others. As new types of equipment are introduced to reduce the amount of heat or energy used to process milk, it is also essential to determine their effects on milk flavor and aroma. In this study, a some of the volatile molecules that contribute to milk aroma in raw and heat-treated milk samples were measured before and after treatment with a microfluidizer, which homogenizes milk at very high pressure. Results showed that microfluidization had minimal or no effects on the amounts of the volatile molecules and all but one were well below the threshold amounts that humans can detect. This study demonstrates the usefulness of screening the volatile compounds found in milk to determine if new equipment will alter the aroma of milk.

Technical Abstract: As innovative types of processing equipment are introduced to milk processing, it is essential to determine their impact on milk aroma, a critical factor to consumer acceptance of the final dairy product. Microfluidization has several applications in the dairy foods industry and is known for its severe homogenization of milk fat. Although severe processing is known to release undesired aromas, there is little information available on the levels of the volatile compounds in milk immediately after microfluidization. The aroma profile of 11 selected volatile compounds found in raw, thermized, pasteurized, and ultra-high temperature (UHT) milk samples were measured before and after microfluidization at 54C at 170 MPa and compared to 2-stage homogenized (15 MPa) samples. Overall, the different milk samples had similar trends in response to homogenization, although levels were lower for acetone and higher for hexanal, heptanal and lower nonanoic acid. The fatty acid volatiles tended to be highest for the 2-stage homogenized samples while no changes were noted for the microfluidized samples, except for lower levels of nonanoic acid. Microfluidized samples tended to be similar to that of the starting milk for hexanal, heptanol, nonanal, and 1-pentanol, although heptanol was higher in UHT milk. Microfluidization decreased 1-pentanol in UHT milk and acetone in all but the UHT samples. Almost all of the volatiles were below the threshold values for human detection except for 2-butanoic acid, which was not significantly different (P > 0.05) for all samples except for the 2-stage homogenized raw milk. Microfluidization had minimal effect on the levels of the 11 volatile compounds presented and suggest that it should not have a direct influence on the aroma profiles of milk.